Abstracts

Rationale: Dravet syndrome is an encephalopathy that begins in the first year of life. Clinical manifestations include intractable epilepsy, cognitive deficits and motor impairments. Around 70-80% of patients have mutations in the SCN1A gene, which encodes the alpha subunit of the type I voltage gated sodium channel. This channel has a key role in the generation of gamma oscillations that are related with cognition. Cortical gamma oscillations can be studied by means of steady-state responses. Our aim was to study the generation of brain oscillations using auditory steady-state responses in patients with Dravet Syndrome. Methods: 4 healthy volunteers and 5 patients with Dravet Syndrome of similar ages were studied. Auditory steady-state responses were evaluated using a tone modulated in amplitude by a sinusoid whose frequency increases linearly ('chirp') from 1 to 120 Hz. Time-frequency transforms were used for the analysis of the evoked responses.Results: The four healthy volunteers showed, as expected, normal auditory steady-state responses, with two ranges of maximal amplitude of the responses around 40 Hz and in the 80-120 Hz range (figure A: Time-frequency analysis; figure C: inter-trial coherence). On the contrary, no auditory steady-state responses within the studied range were found in the 5 Dravet patients (figure B: Time-frequency analysis; figure D: inter-trial coherence).Conclusions: Steady-state responses are severely impaired in patients with Dravet syndrome, suggesting a global impairment in the mechanisms involved in cortical oscillatory activity generation in these patients. Further studies are needed to establish if it could be a useful tool to measure the effect of the treatments.